You seem to have mistaken an online forum for a public place - your right to free speech is still intact, you just weren't speaking in a public forum. If you go pay for space on the web, set up software, and assign yourself status as Moderator, you, too, can freely ban, delete and shush the people logging in there. He pays for the privilege - it's his space. So he's the law in that forum.

Your right in that instance is to go somewhere else to post. Clearly you're exercising it.

The 2nd amendment discussion comes up a lot in most online forums. The discussions will be heated as everyone has their views on the matter. That being said, most of us know that the ranting from all parties leads no where and a Yosemite discussion board is not the best place for expressing said opinions. That sucks that you got banned, only the person who banned you knows exactly why, but steering away people who could otherwise get some very useful information from very knowledgable people is juvenile.